Electron discharge tube



ELEGTRON DISCHARGE TUBE- Filed March 1o, 195e INVEYI'R. JOHAN LODI-:WIJKHENDRIK JONKER' A TTG RNEY.

Patented Mar. 30, 1937 UNITED STATES ELECTRON DISCHARGE TUBE JohanLodewijk Hendrik Jonker, Eindhoven,

Netherlands, assig-nor to N. V. Philips Gloeii lampenfabrieken,Eindhoven, Netherlands Application March 10, 1936, Serial No. 67,999 Inthe Netherlands December 12, 1934 1 Claim.

This invention relates to an electron discharge tube, more particularlyto improvements in electron discharge tubes having two or more grids.

5 The applicant has found that particularly in the case of tubescomprising at least one grid wound with a varying pitch theoperating'conditions in the conventional multigrid tube are not entirelysatisfactory. In such tubes, for example in the case of the so-calledtube with variable mu characteristic, the control grid is gener-allywound with variable pitch, the following grids, for example thescreening grid, the suppressor grid and the like being wound normally.It has been found that with this construction the most favorableconditions are not obtained, this being true for example, when thecontrol grid has a varying pitch between wires and the grid followingafter it or one of the next successive grids is wound with a constant,generally fairly small pitch.

In the case Where the pitch of the conventional grids following thecontrol grid is such as to provide the most favorable operatingconditions opposite the closely spaced turns of a variable pitch grid,this pitch of the following grids would not be such as to provide themost favorable operating conditions opposite the portions of the controlgrid Where the turns of the control grid are more widely spaced. If, forexample in a pentode, the suppressor grid is wound with a normal regularpitch, whereas the control grid has a varying pitch at the portions ofthe control grid where the pitch is Wide, a great number of electronswill pass through to the suppressor grid but cannot pass in anundisturbed manner` through the comparatively small pitch in thesuppressor grid or in any further grid found in the path of theelectrons, with the result that a high space ch-arge may build up whichmay cause the electric properties of the tube to be varied in anundesirable manner. The reverse may also be true. If for example thesuppressor grid is made with a constant wide pitch satisfactory for thewide portions of the control grid, it may be entirely unsatisfactory forthe small pitch portions of the control grid. In this connection forexample, the internal resistance of tubes for special purposes may oftenhave to have especially high values, which may be detrimentally inuencedby the above mentioned phenomena, for although in the above mentionedcases comparatively favorable conditions may be obtained for part of thegrids, this may be offset by other parts of the grid so that as thefinal result the (Cl. Z50-27.5)

construction of the tube is not found to be the most favorable.

It is the principal object of this invention to provide an electrondischarge tube of improved type which overcomes the above difficultiesand can be operated under favorable conditions with respect to the pathof the electrons and which has improved electric properties.

It has been found that the above difficulties can be obviated by thepresent invention. Thus, 10 according to the invention, in an electrondischarge tube comprising two or more grids at least one of which has avaryingpitch the construction of one or more of the remaining grids inthe tube is so altered as to conform with the 15 construction of thefirst mentioned vgrid so that the most favorable conditions are obtainedin connection with the path of the electrons and the resultant electricproperties of the tube.

In a preferred embodiment of the present in- 20 vention an electrondischarge tube, particularly a tube h-aving a variable mucharacteristic, comprises at least two grids wound with a variablepitch. This ensures that for the entire surface of such a grid the mostfavorable conditions 25 as regards the electric properties of the tubecan be obtained.

In addition, the invention is not only applicable to those gridconstructions in which the variability of their construction consists inthe 30 variation of the pitch of the grid itself so that between thewires apertures of different size are obtained, but also to those gridsin which the position of the side rods may bring about alterations inthe path of the electrons through the 35 tube. In this case, thesealterations may be largely compensated for by the side rods of one ofthe following grids being arranged at a given point or being given adetermined diameter.

In order that the invention may be clearly 40 understood and readilycarried into effect it will now be described more fully with referenceto the accompanying drawing in which the single embodiment of theinvention is illustrated very diagrammatically. 45

Referring to the drawing, the electron discharge tube has an electrodemount assembly comprising a cathode I, in the present case an indirectlyheated cathode, of an electron discharge tube is surrounded by grids 2,3 and 4 50 which may be used as the control grid, the screening grid andthe suppressor grid respectively, these electrodes being finallysurrounded by an anode 5. It is readily apparent from the figure thatthe first gridhas a varying pitch 55 10 however, not essential that thepitch of the two grids should extend in exactly the same manner.

While I have indicated the preferred embodiV ments of my invention ofwhich I am now aware and have also indicated only one specic appli- 15cation for which my invention may be employed,V

it will be apparent that my invention by no means limited to the exactforms illustrated or the use indicated, but that many variations may bemade in the particular structure used and t the purpose for which it isemployed without departing from the scope of my invention as set forthin the appended claim.

I claim: Y

An electron discharge tube having an electrode mount assemblycomprisingia'cathode andanode, and at least .threesuccessive gridsbetween said cathode and anode, the grid next to said cathode lhaving avariable pitch and the grid next to the anode having a pitch whichconforms substantially to the pitch of the grid next to the cathode,

the wires of the last two mentioned grids being in substantialalignment.

JOHAN LODEWIJK HENDRIK JONKER.

